There are many technologies for sensing hydrogen, some of them are commercialized. Most of the technologies can be split into two categories—chemical sensors and palladium-based sensors. They use properties of hydrogen to interact with materials, either via chemical reactions as in metal oxide sensors, or by dissolving in Pd and changing the physical properties of Pd—H system. The property of Pd to dissolve and store hydrogen is implemented in many approaches to designs of the sensors, including quartz microbalance sensors, which detect a change in resonance oscillation frequency as the palladium film changes its mass while it absorbs hydrogen. A related patent is U.S. Pat. No. 6,029,500. However, using palladium or similar hydrogen dissolving metals as active coatings results in poor stability of the devices as the metal surface oxidizes with time, and also in case of Pd, it can be poisoned by sulfur or delaminated due to the phase change occurring at high hydrogen concentrations. Thus, it is desired to have a sensor stable in time at various chemical and physical conditions.
Like reference symbols in the various drawings indicate like elements.